Holding apparatus for a dental workpiece

ABSTRACT

A holding apparatus for an in particular dental workpiece comprising a holding element and a fixing device, wherein the workpiece can be fixed to the holding apparatus by a relative movement of the fixing device with respect to the holding element, wherein the fixing device or the holding element has a split sleeve, wherein the inside surface of the split sleeve forms a clamping surface for the workpiece and wherein upon the relative movement of the fixing device with respect to the holding element the workpiece can be braced against the holding device by way of the clamping surface.

The invention concerns a holding apparatus for an in particular dentalworkpiece comprising a holding element and a fixing device, wherein theworkpiece can be fixed to the holding apparatus by a relative movementof the fixing device relative to the holding element. In addition theinvention concerns a set comprising such a holding apparatus and adental workpiece. Furthermore the invention also concerns a processingmachine having such a holding apparatus. In addition the inventionconcerns a process for the production of a holding apparatus and aprocessing machine for carrying out that process.

Various apparatuses like for example CNC machines have been used formany years in dental laboratories for producing or processing dentalworkpieces in an automated procedure. An important aspect in thatrespect is that the dental workpiece which is usually in the form of ablank is securely held so that exact processing of the dental workpieceby way of a processing tool is possible. For that purpose there arealready various holding apparatuses which usually have a kind of holdingelement (also referred to as a holding frame or carrier plate) and afixing device for the workpiece on the holding element.

An example of this can be seen from DE 100 37 531 A1. That discloses anapparatus for the production of dental workpieces. In that case, anopening for a blank is provided in a carrier body. The carrier body canbe gripped in a processing machine with its outside. The blank isconnected only to a part of the opening. A central rectangular openingserves to receive the cylindrical blank. The blank is glued at twomutually opposite surfaces to the corresponding walls of the opening.That adhesive mounting is relatively complicated and expensive andleaves residues behind. In addition an embodiment having anadhesive-free holding arrangement is shown, for example involving amechanical positively locking connection. That is achieved by the blankitself having two mutually opposite mushroom-shaped projections whichengage into an opening. A disadvantage with this variant is that theblank itself must be of a relatively complicated configuration. Inaddition the loading on the blanks in the region of the projections orin the enlarged region is relatively high. With this direct connectionvariant therefore damage to the blank cannot be excluded, in particulardue to the high pressure loading.

A further holding arrangement for workpieces is disclosed in EP 2 026931 B1. In accordance therewith a clamping frame has an opening, whereininwardly freely projecting support portions are provided on the clampingframe. A clamping device is also provided on the clamping frame. Aframe-shaped holding arrangement can be secured to the clamping frame byway of that clamping device. Once again the workpiece is glued or weldedin that holding apparatus. It is preferably held in force-locking and/orpositively locking relationship. It is stated generally that theworkpiece together with the holding arrangement can be fitted fixedlyand non-displaceably in a cutting machining apparatus by means of aclamping device, more specifically on a clamping frame which can beinserted therein. However that specification does not explain howprecisely the force-locking and/or positively locking connection betweenthe workpiece and the holding arrangement is made.

US 2009/0274994 A1 discloses a dental milling machine based on a CNCmachine. In this case the individual blanks are fixed to the holdingframe by way of a projection. The precise fixing mode is not describedin greater detail, rather this involves being able to fit smaller orlarger blanks.

DE 20 2010 001 125 U1 also shows an apparatus for holding and/orgripping blanks serving for the production of dental prostheses. Forthat purpose there is provided an outer annular receiving device havinga receiving opening. The blank can be held in the receiving devicedirectly by way of clamping means or clamping claws. It is however alsopossible for an adaptor to be fitted into the receiving device insteadof a large blank, in which case in turn a blank or a plurality of blanksare mounted to the adaptor. The clamping claws are mounted releasably orinterchangeably to the receiving device. It is possible to use clampingclaws of varying lengths to hold blanks of differing thicknesses. Adisadvantage here is that the clamping claws bear directly against arelatively small region of the blank, whereby a relatively high pressureacts on the blank in that region. That can lead to unwanted deformationor overloading of the blank material.

In addition WO 2013/117540 A1 shows a blank receiving means for a dentalmilling machine. Accordingly there is an outer gripping holder and aninner workpiece holder on which in turn a support projection for theblank is provided. The arrangement further has a clamping device whichpresses the blank against the support projection. The clamping device isreleasably mounted by way of screw bolts to the workpiece holder. Thistherefore involves a clamping action for the blank between the clampingdevice and the support projection. Here too there is the disadvantagethat direct clamping is effected in a small region of the blank and theblank must be of a relatively complicated shape. In addition relativelymany components are required for the fixing action.

DE 41 37 563 C1 is also known, disclosing an apparatus for receivingworkpieces of varying dimensions. Blanks of a differing external contourare gripped between prism carriers. Cam projections are provided foruniform opening at both sides, the projections engaging intosemicircular recesses in a curved body. Due to the curved contour of therecesses the displacement travel that the prism carriers cover isidentical and in each case of the same magnitude, relative to thetheoretical central axis. That therefore gives a curved narrowing ofclamping surfaces. In this case too a relatively large number ofcomponents are required for the fixing action.

DE 10 2010 061 116 A1 also discloses a process for the production ofdental workpieces, wherein a workpiece is connected to a glued frame forfixing in a workpiece holder by way of a clamping action. In that casethe workpiece itself can be provided with a projecting step or with anotch into which a congruent counterpart portion of the clamping deviceengages in the region of an axis in the form of a wedge. That clampingor wedge action in this case is also detrimentally implemented directlyat a relatively small region of the workpiece and can thus cause damagein the workpiece to be held.

Therefore the object of the present invention is to provide a holdingapparatus which is improved over the state of the art or an alternativeholding apparatus. In particular the invention seeks to provide that theholding apparatus is of a structurally simple configuration and a securehold for the workpiece can be guaranteed.

That is achieved by a holding apparatus having the features of claim 1.In accordance therewith it is provided according to the invention thatthe fixing device or the holding element has a split sleeve, wherein theinside surface of the split sleeve forms a clamping surface for theworkpiece and wherein upon the relative movement of the fixing devicewith respect to the holding element the workpiece can be braced againstthe holding device by way of the clamping surface. That split sleevetherefore permits peripheral fixing of the workpiece to the holdingapparatus. Advantageously the securing force is distributed to a largeregion of the workpiece. The holding apparatus according to theinvention can also be used or employed in the state of the art as animproved holding option for a workpiece.

The precise configuration of the split sleeve can be per se of anydesired kind as long as the workpiece is braced to the holding apparatusby the relative movement as between the holding element and the fixingdevice. It is preferably provided however that the split sleeve is of apart-annular configuration around a longitudinal axis with a preferablyaxially directed slit. The slit in that case serves in particular toprovide that, in the bracing situation, the split sleeve is constrictedand thereby the workpiece is clamped fast to the holding apparatus.

It is particularly preferably provided for the split sleeve that theclamping surface of the split sleeve can be applied against theworkpiece and the clamping surface has a first inside diametercorresponding to a loose condition of the split sleeve, wherein theclamping surface can be reduced to a second inside diametercorresponding to a braced condition of the split sleeve by the relativemovement of the fixing device with respect to the holding element with anarrowing of the slit. Particularly if the split sleeve is designed onthe basis of a circular cylinder the constriction of the split sleevecan also be defined by way of the inside diameter instead of by way ofthe internal width.

It is further preferably provided that the holding element and thefixing device have mutually corresponding guide or wedge surfaceswherein the fixing device can be fixed, preferably by wedging, againstthe holding element by the relative movement of the fixing device withrespect to the holding element by way of the guide or wedge surfaceswhich bear against each other. The movement along the guide or wedgesurfaces provides that the clearances which are often present betweenholding element, fixing device and workpiece can be better compensated.In other words, if there are small differences in the actual dimensionsof the components involved, the fixing or wedging action willnonetheless always guarantee a secure stable hold in respect of thefixing device on the holding element and thus the workpiece on theholding apparatus.

In regard to the configuration and arrangement of the split sleeve twodifferent embodiments are discussed in detail in this application.According to a first embodiment it is provided that the split sleeve isprovided separately from the holding element as part of the fixingdevice. According to a second embodiment—which is discussed in greaterdetail hereinafter—the split sleeve is in one piece with the holdingelement. The first embodiment will be discussed inn greater detailhereinafter.

In regard to the first embodiment, the exact design configuration of theguide or wedge surfaces can be per se of any desired nature. For examplethe guide or wedge surfaces can be in the form of planes. Preferablyhowever it is provided that the guide or wedge surfaces are at leastpartially of a conical configuration. In other words, conical means thatthe guide or wedge surfaces are at least partially in the form of asurface of a cone. Besides the pure wedging action, that also permits acentering effect.

In addition it is preferably provided that the guide or wedge surface ofthe holding element is formed by an at least partially conical insidesurface of the holding element. Thus the holding element forms an outercomponent of the holding apparatus, wherein the inside surface forms theguide or wedge surface. In matching relationship therewith it is alsoprovided that the guide or wedge surface of the fixing device is formedby an at least partially conical outside surface of the fixing device.Thus the fixing device forms an internal component of the holdingapparatus.

In principle a purely linear movement is sufficient for making theconnection between the fixing device and the holding element. Inaddition a rotational component may also be involved in the relativemovement. It is sufficient therefore that a dental technician positionsthe holding element, the fixing device and the dental workpiece by hand,and a wedging effect is effected by pushing in or displacing the fittingdevice relative to the holding element whereby at the same time thedental workpiece is clamped fast to the holding apparatus. It ispreferably provided however that the holding apparatus itself also hasadditional guide components so that the relative movement for the fixingaction can be effected in guided relationship.

According to a preferred embodiment it is therefore provided that atleast one preferably at least partially thread-shaped guide is providedin the holding element and the fixing device has at least one noseengaging into the guide, wherein the guide or wedge surfaces of thefixing device and the holding element move relative to each other in theaxial direction and wedge by virtue of rotation of the fixing devicewith the nose engaging into the guide. A reversed configuration (guidein the fixing device and nose on the holding element) is alsoconceivable.

It is further preferably provided that the guide or wedge surface of theholding element defines an opening in the holding element and theopening provides a wide side and a narrow side, wherein the maximumdiameter of the opening on the wide side is greater than the maximumdiameter of the opening on the narrow side.

To cause the axial relative movement for fixing or wedging, it ispreferably provided that the guide has a guide surface which is inclinedrelative to a transverse plane oriented at a right angle relative to thelongitudinal axis, preferably being inclined through an angle of between2° and 15°. To also produce the desired direction for the relativemovement it is preferably provided that the guide surface is inclined inthe direction of the narrow side.

It is per se immaterial where precisely the guide means is provided aslong as the nose can engage into the guide. Thus the guide can certainlybe provided in the central region or in the region of the wide side.According to a preferred variant however it is provided that the guideis provided in the region of the narrow side of the opening in theholding element.

In order to be able to guarantee appropriate positioning when the fixingdevice is put together with the holding element it is preferablyprovided that provided in the holding element is at least one axiallyoriented groove which also forms the inside surface and corresponds tothe at least one nose. More specifically in that case positioning iseffected by the fixing device being guided on the holding element by wayof the nose engaging into the groove whereby the fixing device islinearly axially moveable along the groove in the relative movement.

For user-friendly and intuitive positioning and fixing it is preferablyprovided that the groove and the guide blend into each other whereby thegroove and the guide by the cooperation with the nose of the fixingdevice predetermine the relative movement in the form of a bayonetclosure-like fixing movement for the fixing device on the holdingelement.

Besides the holding element and the fixing device the holding apparatusaccording to the first embodiment can also have a tool for carrying outthe relative movement of the fixing device with respect to the holdingelement. Thus the dental technician does not have to connect only withhis hands the two components consisting of the holding element and thefixing device. It is preferably provided here that the tool hasconnecting elements for connection in positively locking relationship tothe fixing device, wherein the fixing device is at least rotatablerelative to the holding element by the tool.

Accordingly matching counterpart connecting portions in relation to theconnecting elements of the tool can be provided in the fixing device.

In the second embodiment—in which the split sleeve is part of theholding element—it is preferably provided that the fixing device has atleast one clamp with two mutually spaced clamp surfaces—which correspondto the guide or wedge surface of the fixing device—, wherein the clampsurfaces of the fixing device can be applied against mutually spacedcounterpart clamp surfaces arranged in the region of the slit facingaway from the clamping surface—and which correspond to the guide orwedge surface of the holding element.

To permit fixing or wedging between holding element and fixing device ina simple fashion it is preferably provided that the mutually spacedclamp surfaces have a minimum spacing relative to each other, which isless than the spacing between the counterpart clamp surfaces in theloose condition of the split sleeve.

In order to permit the connection to be made at all between holdingelement and fixing device guide portions which are preferably inclinedlyoriented are provided at the clamp surfaces of the fixing device. Forthat purpose it is preferably provided that the counterpart clampsurfaces are moveable relative to each other by the relative movement ofthe clamp with respect to the holding element by the guide portion whichbears against the counterpart clamp surfaces so that with a reduction inthe slit the clamping surface can be reduced to the second insidediameter which corresponds to the braced condition of the split sleeveand in which the minimum spacing of the clamp surfaces relative to eachother is equal to the spacing between the counterpart clamp surfaces.

It is preferably further provided that a plurality of separateworkpieces can be braced to the holding apparatus by way of respectivesplit sleeves. In this case there can be an associated clamp for eachsplit sleeve. In other words the fixing device has at least two clampswhich are preferably arranged regularly relative to each other, whereineach clamp respectively corresponds to one of at least two split sleevesprovided in the holding element.

In order also to be able to clamp a plurality of workpieces fast asquickly as possible it is particularly preferably provided that thefixing device having a plurality of clamps is in one piece. Thus aplurality of workpieces can be simultaneously braced to the holdingapparatus by the relative movement of that single one-piece fixingdevice. Preferably the fixing device is of a star-shaped configurationfor that purpose.

The scope of protection of the holding apparatus as set forth in claim 1relates only to the at least two-part holding apparatus per se. It ishowever certainly also possible to provide that at least one workpiece,preferably a plurality of prefabricated workpieces, is also included inthe scope of supply. For that reason protection is also claimed for aset comprising a holding apparatus according to the invention and atleast one dental workpiece. In that respect that workpiece can be ofwidely varying shapes. For ease of production and mounting the workpieceis in the form of a right circular cylinder.

Protection is also claimed for a processing machine, in particular a CNCmachine, comprising a processing tool and a holding apparatus accordingto the invention for a workpiece. To permit a movement of the gripped orclamped workpiece it is preferably provided that the processing machinehas a moveable positioning device which is preferably of a cardanjoint-like configuration, wherein the holding apparatus can bereleasably fixed on the positioning device. The workpiece can then beprocessed in a dental workpiece production mode by way of the processingtool using that machine.

In order to not only acquire protection for the specific holdingapparatus protection is also claimed for a process for the production ofa holding apparatus according to the invention in a processing machine,in particular in a CNC machine. That process can be implemented in thesame processing machine in which processing of the workpiece is alsoeffected.

Here it is particularly preferably provided that in a holding apparatusproduction mode of the processing machine the holding element and thefixing device of the holding apparatus can be produced, preferablymilled, from workpieces clamped in the processing machine. That ispreferably effected by the holding apparatus production mode beingperformed on the basis of data of the holding element and the fixingdevice, which are stored in a memory and which can be read and executedby the processing machine.

Protection however is not only requested for the processing machine witha holding apparatus according to the invention, but also for aprocessing machine for carrying out the process for the production of aholding apparatus. In that respect it is provided that the holdingapparatus production mode for production of the holding apparatus isstored in a memory of the processing machine, wherein the holdingapparatus production mode can be enabled by input of a code. Thus inregard to future deliveries of processing machines the correspondingholding apparatus production mode can already be stored in theprocessing machine. If the owner or purchaser of that processing machinethen also desires his own production of the holding apparatus accordingto the invention he can cause the corresponding holding apparatusproduction mode to be enabled.

Alternatively however it is also conceivable for a purchaser toretro-fit his already existing processing machine with a holdingapparatus production mode. For that reason protection is also claimedfor a data carrier on which the production process according to theinvention is stored in the form of data which can be read by aprocessing machine and which can be executed as the holding apparatusproduction mode for production of the holding apparatus.

Further details and advantages of the present invention will bedescribed more fully hereinafter by means of the specific descriptionwith reference to the embodiments by way of example illustrated in thedrawings in which:

FIGS. 1a through 1c show variants of a dental workpiece,

FIG. 2 shows a diagrammatic section through a first embodiment of aholding apparatus,

FIGS. 3a and 3b show different views of a fixing device,

FIGS. 4a through 4c show different views of a holding apparatus whenviewing from the narrow side,

FIGS. 5a through 5d show different views of the holding apparatus whenviewing from the wide side,

FIGS. 6a through 6d show the holding apparatus in the loose condition ofthe split sleeve,

FIGS. 7a through 7d show the holding apparatus in the braced conditionof the split sleeve,

FIGS. 8a through 8e show various views of a tool,

FIGS. 9a and 9b show views of a second embodiment of a holdingapparatus,

FIGS. 10a and 10b show views of the fixing device,

FIGS. 11a and 11b show views of the workpiece,

FIGS. 12a through 12c show views of the holding apparatus with thebraced split sleeve,

FIGS. 13a and 13b diagrammatically show the difference between the looseand the braced split sleeve,

FIGS. 14a through 17c show views of a further variant of the secondembodiment,

FIG. 18a shows a processing machine with a diagrammatically illustratedopen-loop or closed-loop control unit,

FIG. 18b shows the detail of the positioning device of FIG. 18a , and

FIGS. 19a and 19b show the processing machine with a holding apparatusaccording to the second embodiment.

The fundamental idea of the present invention is based on the fixing ofgeometrically simple dental workpieces. Those dental workpieces 2 arepreferably made from zirconium dioxide. It is however also possible touse other materials like for example plastics, sintered metals, mixedmaterials and so forth. A preferred variant of such a zirconium block ordental workpiece 2 is shown in FIG. 1a , in accordance with which thedental workpiece 2 is of a circular-cylindrical configuration and has nofurther steps or recesses, by way of which the dental workpiece 2 issupported or which would permit fixing. Fixing to a holding apparatus 1is thereby effected purely in force-locking relationship. Thatforce-locking connection is made by way of the peripheral surface U ofthe dental workpiece 2. FIGS. 1b and 1 c also show alternative possibleconfigurations of the dental workpiece 2 on the basis of a rectangularbase surface or a triangular base surface.

FIG. 2 diagrammatically shows the fixing of a dental workpiece 2 to aholding apparatus 1. For that purpose the holding apparatus 1 has twocomponents, namely the holding element 3 and the fixing device 4. In thefixing operation firstly the workpiece 2 is introduced into the opening8 in the holding element 3. At the same time the fixing device 4 is alsopre-positioned. In that case as shown in FIG. 2 the fixing device 4 isin the form in section of a simple wedge. In that case the fixing device4 has a guide or wedge surface K₄ corresponding to the guide or wedgesurface K₃ forming the inside surface of the holding element 3. Thatguide or wedge surface K₃ of the holding element 3 provides that themaximum diameter D_(B) of the opening 8 on the wide side B of theholding element 3 is larger than the maximum diameter D_(S) of theopening 8 on the narrow side S. Accordingly the opening 8 narrows fromthe wide side B towards the narrow side S (this corresponds to the firstembodiment). By virtue of a relative movement R of the fixing device 4in the direction of the longitudinal axis L the guide or wedge surfacesK₃ and K₄ move against each other whereby the peripheral surface U ofthe dental workpiece 2 is braced or clamped between the clamping surfaceM, that is remote from the guide or wedge surface K₄, of the splitsleeve of the fixing device 4 and the holding element 3. In that case asshown in FIG. 2 direct contact occurs on the right-hand side between theworkpiece 2 and the holding element 3. Naturally however it is alsopossible—as also shown in later embodiments—that the fixing device 4 isof a configuration or is arranged in the form of a partial ring (andthus also at the right-hand side) around the dental workpiece 2. Thesimplest functional variant of the holding apparatus 1 is however shownin FIG. 2. Due to the relative movement R of the fixing device 4 in thedirection of the arrow therefore the workpiece 2 goes from a loosecondition Z₁ into a braced condition in which the split sleeve is in afixed or wedged condition Z₂ on the holding apparatus 1. In that bracedcondition Z₂ the space for the dental workpiece 2 within the holdingapparatus 1 is constricted in such a way that the dental workpiece 2 isbraced to the holding apparatus 1 and is thus clamped or gripped inforce-locking relationship.

FIGS. 3 through 8 e show a first embodiment of a holding apparatus 1. Incomparison with the structure shown in FIG. 2 it can be seen from FIG.3a that the fixing device 4 is in the form of a partial ring and thusforms the split sleeve. For that purpose the split sleeve of the fixingdevice 4 has a slit 5. That slit 5 does not have to be continuoustherethrough but may also be only of such a length as to permit areduction in the inside diameter D. That slit 5 also does not have to bein the form of an opening or “free space” but can also be filled with ayielding material. In addition that slit 5 does not have to be orientedprecisely in the axial direction but can certainly also be orientedinclinedly and thus not parallel to the longitudinal axis L. Preferablyhowever that slit 5 extends continuously through the sleeve and isoriented in the axial direction. At the outside or at the outsidesurface the fixing device 4 has the guide or wedge surface K₄. Theclamping surface M is provided at the inside surface of the fixingdevice 4. The clamping surface can in principle be of a continuouslyflat or level configuration so that in the braced condition Z₂ it bearsthroughout flat or flush against the workpiece 2. The specificembodiment of FIG. 3a however has recesses 20. Those recesses 20 orturned grooves provide for a better hold for the dental workpiece 2.Those recesses 20 can also be of a spiral configuration or can be ofother shapes which serve for the purpose of better fixing.

FIG. 3b shows a side view of the fixing device 4. The conicalconfiguration of the guide or wedge surface K₄ can be particularly wellseen here. Preferably the guide or wedge surface K₄ (like also the guideor wedge surface K₃) is inclined relative to the longitudinal axis Lthrough an angle β of between 1° and 15°, preferably between 2° and 10°.

FIG. 4a shows the holding apparatus 1 with a view on to the narrow sideS of the holding element 3. Provided in the holding element 3 are atotal of five openings 8 which respectively form an inside, guide orwedge surface K₃ of the holding element 3. In addition the guidesurfaces F of the guide 6 can be seen in FIG. 4a . They correspond tothe noses 7 on the fixing device 4. The grooves 9 in the holding element3, oriented in the axial direction, can also be seen.

It is also possible to see the slit 5 in each fixing device 4. Arrangedregularly at the rim surface of the holding element 3 are the clampingsurfaces 18, by way of which the entire holding apparatus 1 isreleasably fixed to a positioning device 15 of a processing machine 13.

FIG. 4b shows the section i-i through the holding apparatus 1 of FIG. 4a. It can be seen that the guide 6 is provided at the narrow side S ofthe holding element 3. In this arrangement the guide 6 merges into thegroove 9. It is also possible to see the guide surface F of the guide 6,which is inclined in the direction of the narrow side S through theangle α relative to the transverse plane Q oriented at a right angle tothe longitudinal axis L. That provides that—when the nose 7 of thefixing device 4 bears against the guide surface F upon rotation of thefixing device 4 relative to the holding element 3—a necessary relativemovement R of the fixing device 4 in the direction of the longitudinalaxis L towards the narrow side S takes place, whereby the wedge or guidesurfaces K₃ and K₄ wedge together.

FIG. 4c shows a perspective view of the holding apparatus 1 againviewing in the direction of the narrow side S. It can be seen that thefixing devices 4 are still in the loose condition Z₁. A slight wedgingeffect between the guide or wedge surfaces K₃ and K₄ may however alreadyexist. That however is still not sufficient to adequately clamp a dentalworkpiece 2 (not shown in this FIG. 4c ) within the fixing device 4.

FIGS. 5a through 5d show the same embodiment and the same condition Z₁as FIGS. 4a through 4c . FIG. 5a however shows the holding element 3together with the fixing device 4 from the wide side B. The counterpartconnecting portions 19 which are provided in the fixing device 4, forthe tool 10 which is also shown hereinafter, can also be seen from thewide side B.

FIG. 5b shows a side view of the holding element 3, clearly illustratingthe clamping surfaces 18.

FIG. 5c shows the section ii-ii through the holding apparatus 1 of FIG.5a . It is possible to see the mutually contacting conical guide orwedge surfaces K₃ and K₄ of the holding element 3 and the fixing device4 respectively.

FIG. 5d shows a perspective view of the holding apparatus 1 viewing inthe direction of the wide side B. The transition from the axiallyoriented groove 9 into the guide 6 which is oriented slightly inclinedlyrelative to the transverse plane Q can be clearly seen. The relativemovement R of the fixing device 4 with respect to the holding element 3is shown in broken line in this FIG. 5d , wherein that positive guidanceis effected by the nose 7 of the fixing device 4, that corresponds tothe groove 9 and the guide 6. That relative movement R forms a bayonetclosure-like fixing movement for the fixing device 4 on the holdingelement 3.

FIG. 6a shows the holding apparatus 1 in a loose condition Z₁ of thefixing device 4. Nonetheless a dental workpiece 2 is already disposed inthe holding apparatus 1.

It can be seen from FIG. 6b that the slit 5 in the split sleeve of thefixing device 4 is still opened. As a result there is still no adequateclamping between the dental workpiece 2 and the holding apparatus 1.FIG. 6b also shows that the holding apparatus 1 is formed by the fixingdevice 4 and the holding element 3. The holding apparatus 1 in turnforms the set 12, together with the at least one dental workpiece 2.

FIG. 6c shows the section iii-iii through the set 12 of FIG. 6b . Theclamping surface M, which can bear against the workpiece 2, of the splitsleeve of the fixing device 4 is still of a first inside diameter D₁corresponding to a loose condition Z₁ of the fixing device 4.

FIG. 6d also shows that larger inside diameter D₁ when the slit 5 isstill open.

In comparison FIGS. 7a through 7d show the holding apparatus 1 in thewedged condition Z₂ of the fixing device 4 on the holding element 3. Ascan be seen in that respect from FIG. 7a the slit 5 of the split sleeveof the fixing device 4 has already constricted whereby the clampingsurface M bears flush against the peripheral surface U of the workpiece2. That constriction of the slit 5 can also be seen from FIG. 7b wherebythe clamping surface M of the fixing device 4 is reduced to a secondinside diameter D₂ corresponding to a braced condition Z₂ of the splitsleeve of the fixing device 4. That reduced second inside diameter D₂can also be seen from FIGS. 7c and 7d . In particular a comparison ofFIGS. 6d and 7d -shown diagrammatically and in exaggerated form—showsthe change in diameter between the loose condition Z₁ and the bracedcondition Z₂.

FIGS. 8a through 8e show various views of the tool 10 having theconnecting elements 11 in the form of projections. Those connectingelements 11 correspond with the counterpart connecting portions 19provided in the fixing device 4. When such a tool 10 is fitted to afixing device 4 for example as shown in FIG. 6a then the nose 7 is alsomoved along the guide surface F of the guide 6 by rotation on the tool10 so that the fixing device 4 moves relative to the holding element 3in the direction of the narrow side S and as a result the clampingsurface M of the fixing device 4 is constricted, with clamping of thedental workpiece 2.

FIGS. 9a through 17c show a second embodiment of a holding apparatus 1.In this second embodiment the split sleeve is in one piece with theholding element 3.

FIG. 9a as a plan view on to the holding element 3 shows that the splitsleeve substantially comprises the two bow portions 26 and the slit 5.In this case the holding element has in total six such split sleeveseach having two bow portions 26. The inside surface of each split sleeveforms a clamping surface M for the workpiece 2. A certain flexibility ofthe bow portions 26 is guaranteed by the opening 27. A counterpart clampsurface G is provided on each bow portion 26 in a region remote from theclamping surface M. In the loose condition Z₁ of the split sleeve asshown in FIG. 9a the counterpart clamp surfaces G of two bow portions 26of a split sleeve are spaced from each other by the spacing A_(G). FIG.9b shows a perspective view of the same holding element 3.

FIGS. 10a and 10b show the fixing device 4 having a plurality of clamps24 each having two clamp surfaces H. The total of six clamps 24 are inone piece and together form the fixing device 4. The clamp surfaces H ofthe clamps 24 are at a minimum spacing A_(H) relative to each other. Theclamp surfaces H together with the guide portions 25 form the guide orwedge surfaces K₄ of the fixing device 4. Those guide portions 25 are inthe form of rounded-off or inclined edge regions of the fixing device 4.

FIGS. 11a and 11b show a workpiece 2 which can be braced to the holdingapparatus 1.

Bracing of a workpiece 2 to the holding apparatus 1 in accordance withthe second embodiment is effected by the desired number of workpieces 2firstly being fitted into a holding element 3 as shown in FIG. 9a , intothe openings 8 provided for same. As the split sleeves of that holdingelement 3 are still in the loose condition Z₁ introduction of theworkpieces 2 into the openings 8 is possible without any problem. Thatinsertion of the workpiece is shown in FIG. 13a , wherein the spacingA_(G) between the counterpart clamp surfaces G and thus the size of theslit 5 are shown in exaggerated form. It can also be seen that theworkpiece 2 does not (or scarcely) contact the holding element 3 as theinside diameter D₁ in the loose condition Z₁ is still larger.

As soon as the desired number of workpieces 2 is inserted in the holdingelement 3 the preferably star-shaped fixing device 4 is introduced intothe center of the holding element 3. In that case the guide portions 25initially contact the counterpart clamp surfaces G of the split sleevesof the holding element 3. By virtue of the relative movement R of thefixing device 4 in the direction of the longitudinal axis L the bowportions 26 of the split sleeves are moved towards each other by virtueof the inclined guide portions 25 until the counterpart clamp surfaces Gcontact the clamp surfaces H. As a result the spacing A_(G) between thecounterpart clamp surfaces G of a split sleeve corresponds to theminimum spacing A_(H) between the clamp surfaces H, as shown in FIG. 13b. As the bow portions 26 move towards each other due to that relativemovement R the inside diameter D₂ of the split sleeve is reduced wherebythe workpiece 2 is braced by way of the peripheral surface U against theclamping surface M of the split sleeve. FIGS. 12a through 12c show thecondition when a total of six workpieces 2 are braced in a holdingelement 3 by way of a fixing device 4. It is particularly advantageouswith this structure that all workpieces 2 can be simultaneously bracedto the holding apparatus 1 by a single relative movement R of the fixingdevice 4 relative to the holding element 3. It is also possible for someopenings 8 to be left free and also for example only a single workpiece2 to be fixed in such a holding element 3.

FIGS. 14a through 17c show a further variant of the second embodiment,wherein only one workpiece 2 can be braced in this holding element 3. Inthe same fashion as with the first variant, this arrangement has a splitsleeve with two bow portions 26 together with counterpart clamp surfacesG (see FIGS. 14a and 14b ). The fixing device 4 in FIGS. 15a and 15b isformed by a clamp 24 having two mutually spaced clamp surfaces H. Theworkpiece 2 has a rectangular base surface with rounded-off side edges.As soon as that workpiece 2 is fitted into the opening 8 in the holdingelement 3 the fixing device 4 (clamp 24) is inserted as shown in FIGS.17a through 17c by way of the guide portions 25 until the clamp surfacesH and the counterpart clamp surfaces G are in contact whereby theclamping surface M holds the workpiece 2 to the holding apparatus 1. Inthat case the entire inside diameter of the clamping surface M is notreduced, but the clamping surface M is pressed more intimately againstthe workpiece 2 by the extent of the reduction in the size of the slit 5whereby the workpiece is sufficiently firmly braced to the holdingapparatus 1.

FIG. 18a shows a processing machine 13 in the form of a CNC machine. Inaccordance with the detail view in FIG. 18b that CNC machine has apositioning device 15. The positioning device 15 can have a plurality ofcomponents arranged in a cardan joint-like fashion. More specificallyprovided as the innermost structural unit is a holding ring 23 to whicha holding apparatus 1 or a set 12 can be releasably fixed by way of thefixing means 22. The dental workpieces 2 which are held to thepositioning device 15 by way of the holding apparatus 1 and which aremoveable by that positioning device 15 can then be worked or milled bythe processing tool 14. In that case the processing operation iscontrolled or regulated by way of the open-loop or closed-loop controlunit 21 diagrammatically shown in FIG. 18a . For that purpose the dentalworkpiece production mode M₂ can be executed by the open-loop orclosed-loop control unit 21. In addition however it is also possible fora holding apparatus production mode P₁ to be implemented by theopen-loop or closed-loop control unit 21. For that purpose data N(preferably in the form of CNC files) are stored in a memory 16 of thecontrol unit 21. In order now to produce the holding apparatus 1 itselfin the processing machine 15 the holding apparatus production mode P₁can be enabled by the input of a code. As an alternative variant it isalso possible that the production mode P₁ can be retro-fitted to analready existing processing machine 13 by way of a data carrier 17 (forexample a USB stick) on which the executable data N (CNC files) arestored. FIGS. 19a and 19b show the positioning device 15 with theclamped holding apparatus 1 in accordance with the second embodiment.

The invention can also be summarized and described once again using thefollowing different words:

The fixing device 4 can also be referred as a conical counterpartportion in relation to the holding element 3 or as a clamping ring. Thatclamping ring can best be seen in FIG. 3a . Disposed on the outside ofthat fixing device 4 is the conical surface as the guide or wedgesurface K₄ corresponding to a milled-out orifice or opening 8 in theholding element 3 which is in the form of a carrier plate. In the centerthe fixing device 4 has a bore or opening which does not necessarilyhave to be concentrically positioned. Preferably it is additionallyprovided that recesses 20 or turned-in grooves are provided at theinside surface of the fixing device 4, the recesses or grooves beingintended to later provide for a better hold for the dental workpiece.The fixing device 4 preferably has two noses which permit assembly ofthe fixing device 4 and the holding element 3 only in given positions,more specifically when the noses 7 and grooves 9 are disposed preciselyone above the other. When then the two parts are assembled until theconical surfaces or wedge surfaces K₃ and K₄ are in contact, a furtherfeature of the fixing device 4 comes into play. More specifically on oneside that fixing device 4 has an opening in the form of a slit 5 whichpreferably extends from the upper edge to the lower one. Thus theclamping ring (fixing device 4) is peripherally opened. When now thefixing device 4 in the inserted position is turned by means of a wrench(tool 10) which is shown in FIGS. 8a through 8d by way of the auxiliarybores (counterpart connecting portions 19) that entails a reduction inthe periphery of the clamping ring (inside diameter D of the clampingsurface M of the fixing device 4 is reduced in size). That occurs forthe reason that the noses 7 of the fixing device 4 slide over thespiral-shaped surface (guide surface F) of the holding element 3 andthus pull it in the direction of the conical narrowing. In the directionof rotation therefore the spacing between the front side of the holdingelement 3 and the surface of the guide 6 increases. To permit uniformtightening there are provided at least two noses 7 which are preferablyin precisely opposite relationship. However the situation should not beexcluded that more noses 7, in matching relationship also with thegrooves 9 and the guides 6, are provided. They also do not have to beuniformly distributed over the periphery. The same applies to the slit5. Accordingly FIG. 3 only shows a preferred variant. Thus it may bereadily possible that the slit 5 does not peripherally open the fixingdevice 4 at one side in the longitudinal direction L, but for thatpurpose the arrangement has a plurality of slits 5. It will beappreciated that for such a variant the holding element 3 must alsoagain have the necessary structural features for satisfactory interplay.

A further substantial part of a set 12 is the block (dental workpiece 2)which preferably comprises zirconium (see in particular FIG. 1a ). Thepreferred variant is a cylindrical block without any additional materialremovals, like for example grooves extending along the periphery orregion-wise protrusions. That block is then pushed into the bore of theclamping ring (fixing device 4). That can happen at the moment in timewhen the clamping ring is not yet disposed in the carrier plate (holdingelement 3) or when the clamping ring is positioned in the carrier platebut is not yet tightened, for which reason there has not yet been areduction in periphery. Referring to FIG. 6a it will be seen how theworkpiece 2 is pushed into the fixing device 4 and how there is stillspace along the periphery between the fixing device 4 and the workpiece2. When now the fixing device 4 is rotated in the inserted position theinside diameter D of the fixing device 4 is reduced and bears around thein this case periphery of the dental workpiece 2. That can be clearlyseen from FIG. 7c . It can also be clearly seen that the pressure forceproduced by the cone is transmitted to the dental workpiece 2 only overcertain parts of the surface of the fixing device 4. These are thoseregions which do not have any turned recess or the like. As rotation ofthe fixing device 4 always produces a similar pressure force which isthen transmitted to the dental workpiece 2 the efficiency of the holdingapparatus 1 can be determined by the configuration of the turnedrecesses therein. If the turned recesses or grooves 20 are to bedispensed with, the pressure force is distributed uniformly over theentire contact region. Thus, the force acting thereon, if only a smallpart of the surface of the dental workpiece 2 is considered, isrelatively low. If now however the arrangement has turned grooves orrecesses 20 which reduce the contact surface to half then the samepressure force as in the above-mentioned case is however now distributedto half the surface area. If now once again a part of the dentalworkpiece 2, of the same size as previously, is considered, being actedupon with the pressure force, then that gives a holding force which istwice as great. With a certain force there is however inevitablydeformation of the dental workpiece 2. That may happen intentionally butalso unintentionally. A slight degree of deformation promotes stabilityin the axial direction. However, the block which is reduced in volumeafter a processing operation is region-wise weakened and thus moreunstable. The variants shown in FIGS. 3 through 13 a always relate to acircular-cylindrical block. With the dimensioning and the structuralconfiguration being right however that principle can also be transferredto other blocks (dental workpieces 2) of polygonal cross-section (seeFIGS. 14a through 17c ).

The holding element 3 preferably comprises PMMA and the fixing devicePOM. In principle however it is also possible to use any other materialswhich are also suitable for fulfilling the function involved. Thus theholding element 3 can be made for example from a high-grade steel andthe fixing device 4 from aluminum. Preferably the material of the fixingdevice 4 is always softer and thus more easily deformable than theholding element 3.

In relation to FIG. 18a it should be once again explained that thenecessary components of the invention can be made available to acustomer in the form of a holding apparatus 1. It can however also beprovided that the holding element 3 and the fixing device 4 are suppliedto the customer as a pure blank, that is to say without conicalsurfaces, milled-out noses and so forth. If the customer should alreadybe in possession of a processing machine 13 of the present applicant, itis then possible for the customer to clamp those blank blocks in theprocessing machine 13 and to independently produce the parts accordingto the invention of the holding apparatus 1. For that purpose thecustomer then only has to buy in the data carrier 17 with the data N(CNC files) and the blank blocks or to enable the holding apparatusproduction mode P₁ already stored in the processing machine 13, by theinput of a code which is to be purchased.

Both embodiments show a holding apparatus 1 with which workpieces 2(zirconium blocks) can be clamped fast in force-locking relationship. Inthat respect the illustrated options are of such a design configurationthat the clamping force is applied to a large part of the peripheralsurface (peripheral surface U). The basic idea is that the blocks(workpieces 2) are firstly inserted into the holding apparatus 1. Byvirtue of the fact that the latter is produced with a yieldingstructure, preferably of POM, and has a relatively narrow split sleeve,the holding apparatus 1 is correspondingly flexible and then also adaptsto the blank (workpiece 2). That is also the case if the blank should beslightly larger than the opening 8 in the holding apparatus 1.

Especially in regard to the second embodiment (see FIGS. 9a through 13b) it is to be stressed that the clamping wedge member (fixing device 4in the form of the clamp 24) can be inserted as soon as the workpieces 2are fitted in place. In that respect the clamping wedge is of such aconfiguration that it conically converges on the top side and theunderside (guide portion 25) so that it can be more easily pressed intoplace. The operation of pressing it in is effected here only by means ofmanual force. Depending on how wide the projecting projections are orhow small the minimum spacing A_(H) is the clamping force is higher orlower. The correspondingly wider that they are, then the correspondinglyhigher is also the clamping force exerted on the blank. With thisvariant care should be taken to ensure that two workpieces 2 are alwaysclamped in mutually opposite relationship as otherwise the clampingmechanism is too unstable. If there should be a wish to clamp only oneworkpiece 2 then a “blind plug” should be inserted on the other side.The clamping wedge is preferably made from PMMA as that material hasgood sliding capabilities. In general it is to be stated in this respectthat other materials which achieve the aim of fixing can also be usedfor each part. The illustrated configuration affords space for sixblanks, in which respect there can also be more or fewer. The number isthen limited upwardly only by the amount of space required.

In the further variant (FIGS. 14a through 17c ) of the second embodimentthe blank is no longer of a round shape but is of a substantiallycuboidal shape. It will be seen that the clamping mechanism is based onthe same principle as the first variant of the second embodiment. Inthis case, a fixed guide/abutment for the blank is provided on the lowerside of the holding element 3, that faces away from the slit 5. Theclamping force is then again applied on the upper side by way of theclamping wedge member (clamp 24). In that case the clamp surfaces H ofthe clamping wedge member are of substantially the same geometry as inthe first variant. Naturally that also relates to those significant andfunctional regions of the wedge member. In this variant also the block,preferably the zirconium block, is again fitted into the clamping block(holding element 3) and then the clamping wedge member is pushed in bymanual force.

Both variants of the second embodiment are so designed that the blank isgripped over a large surface area and that “peripheral embrace” isinterrupted only at one location (slit 5). Precisely that location issuch that the clamping wedge member tries to reduce the open location inthe peripheral embrace and thus a peripheral force is exerted on theblank. A further advantage here is that the wedge member does not comedirectly into contact with the blank and no tools are required for theclamping effect. That system is thus highly user-friendly.

In the ideal case the blanks (workpieces 2) are of the same height asthe clamping mechanism (holding apparatus 1) so that in use allcomponents can simply be placed on a table and all pushed together. Ifthe blanks are to be lower or higher a spacer disc can be placedtherebeneath to permit a central position for the blank in the clampingblock.

The entire set 12 can then be gripped in a milling system (processingmachine 13). Depending on whether individual working operations ormulti-component dental operations are to be carried out it is possibleto choose between the different variants.

LIST OF REFERENCES

-   1 holding apparatus (clamping block or clamping mechanism)-   2 workpiece (blank)-   3 holding element (holding frame or carrier plate)-   4 fixing device (clamping wedge member)-   5 slit-   6 guide-   7 nose-   8 opening-   9 groove-   10 tool-   11 connecting elements-   12 set-   13 processing machine-   14 processing tool-   15 positioning device-   16 memory-   17 data carrier-   18 clamping surfaces-   19 counterpart connecting portions-   20 recesses-   21 open-loop or closed-loop control unit-   22 fixing means-   23 holding ring-   24 clamp-   25 guide portion-   26 bow portion-   27 opening-   R relative movement-   K₃ guide or wedge surface on the holding element-   K₄ guide or wedge surface on the fixing device-   L longitudinal axis-   M clamping surface-   Z₁ loose condition-   Z₂ wedged condition-   D diameter of the clamping surface-   D₁ inside diameter in the loose condition-   D₂ inside diameter in the wedged condition-   F guide surface-   Q transverse plane-   α angle of the guide surface-   β angle of the guide or wedge surfaces-   B wide side-   S narrow side-   D_(B) maximum diameter wide side-   D_(S) maximum diameter narrow side-   P₁ holding apparatus production mode-   P₂ dental workpiece production mode-   N data-   U peripheral surface-   H clamp surfaces-   G counterpart clamp surfaces-   A_(H) minimum spacing of the clamp surfaces-   A_(G) spacing of the counterpart clamp surfaces

1. A holding apparatus for an in particular dental workpiece comprisinga holding element and a fixing device, wherein the workpiece can befixed to the holding apparatus by a relative movement of the fixingdevice with respect to the holding element, wherein the fixing device orthe holding element has a split sleeve, wherein the inside surface ofthe split sleeve forms a clamping surface for the workpiece and whereinupon the relative movement of the fixing device with respect to theholding element the workpiece can be braced against the holding deviceby way of the clamping surface.
 2. A holding apparatus as set forth inclaim 1, wherein the split sleeve is of a part-annular configurationaround a longitudinal axis with a preferably axially directed slit.
 3. Aholding apparatus as set forth in claim 2, wherein the clamping surfaceof the split sleeve can be applied against the workpiece and theclamping surface has a first inside diameter corresponding to a loosecondition of the split sleeve, wherein the clamping surface can bereduced to a second inside diameter corresponding to a braced conditionof the split sleeve by the relative movement of the fixing device withrespect to the holding element with a narrowing of the slit.
 4. Aholding apparatus as set forth in claim 1, wherein the holding elementand the fixing device have mutually corresponding guide or wedgesurfaces, wherein the fixing device can be fixed, preferably by wedging,against the holding element by the relative movement of the fixingdevice with respect to the holding element by way of the guide or wedgesurfaces which bear against each other.
 5. A holding apparatus as setforth in claim 1, wherein the split sleeve is provided separately fromthe holding element as part of the fixing device.
 6. A holding apparatusas set forth in claim 5, wherein the guide or wedge surface of thefixing device is formed by an at least partially conical outside surfaceof the fixing device.
 7. A holding apparatus as set forth in claim 1,wherein the split sleeve is in one piece with the holding element.
 8. Aholding apparatus as set forth in claim 7, wherein the fixing device hasat least one clamp with two mutually spaced clamp surfaces—whichcorrespond to the guide or wedge surface of the fixing device, whereinthe clamp surfaces of the fixing device can be applied against mutuallyspaced counterpart clamp surfaces arranged in the region of the slit andfacing away from the clamping surface—which correspond to the guide orwedge surface of the holding element.
 9. A set comprising a holdingapparatus as set forth in claim 1 and at least one dental workpiecewhich is preferably of a circular cylindrical shape.
 10. A processingmachine, in particular a CNC machine, comprising a processing tool and aholding apparatus as set forth in claim 1 for a workpiece.
 11. Aprocessing machine as set forth in claim 10, wherein the processingmachine has a moveable positioning device which is preferably of acardan joint-like configuration, wherein the holding apparatus can bereleasably fixed to the positioning device.
 12. A process for theproduction of a holding apparatus in a processing machine, in particularin a CNC machine, wherein workpieces are clamped into the processingmachine and wherein in a holding apparatus production mode of theprocessing machine the holding element and the fixing device of theholding apparatus as set forth in claim 1 are produced, preferablymilled, from said workpieces.
 13. A process as set forth in claim 12,wherein data which can be read and executed of the holding element andthe fixing device are stored in a memory, said data are read out in theholding apparatus production mode and the holding apparatus productionmode is carried out on the basis of said data.
 14. A processing machine,in particular a CNC machine, for carrying out a process as set forth inclaim 12, wherein the holding apparatus production mode for productionof the holding apparatus is stored in a memory of the processingmachine, wherein the holding apparatus production mode can be enabled byinput of a code.
 15. A data carrier on which the process as set forth inclaim 12 is stored in the form of data EN-which can be read by aprocessing machine and which can be executed as a holding apparatusproduction mode for production of the holding apparatus.